A several-year study of distribution, phytocoenological differentiation, floristic composition and structure of ruderal flora and vegetation and relevant anthropogenic influence was conducted at Pančevački Rit in Serbia.Ten clearly distinctive ruderal communities were identified in the study, including the newly formed community Matricario-Helianthetum annuae. This community is a unique combination of transitional ruderal and agrestal vegetation developing spontaneously in close vicinity of intensively cultivated agricultural fields, in which sunflower (Helianthus annuus L.), an annual crop, appears and persists subspontaneously and often massively, rendering a physiognomical character to ruderal habitats in which ephemeral ruderal weed vegetation often develops, consisting predominantly of annual plants of Sisymbrion officinalis R.Tx., Lohm. et Prsg.1950.
The effects of PAR and temperature on induction of Chl a fluorescence were observed on leaves of 20 plant species in their natural environments. Light affects the acceptor side of PS2. Temperature regulation of PS2 activity proceeds by affecting the RC and acceptor side of PS2. The impact of higher temperature can be attributed to greater fluidity of the thylakoid membranes. Photosynthetically active radiation and temperature under the given conditions are in highly significant positive correlation, so it is not clear whether this impact is due to individual or complementary mechanisms of PAR and/or temperature affecting photosynthetic processes in the thylakoid membranes. Also, it is not clear whether species specificity has any significance in the plant photosynthetic response to changes of PAR and temperature. Changes of PAR and temperature during induction of Chl a fluorescence do not affect Pindex, as a parameter of total photosynthesis
Effects of the metribuzin herbicide on soil microorganisms were investigated Trials were set up on a chernozem soil in laboratory environment. Metribuzin application rates were 0.3, 0.6, 1.2 and 2.4 mg a.i./500g air-dry soil at 10?C, 20?C and 30?C. Soil respiration (amount of released CO2) and abundance of total microflora, fungi, actinomycetes, cellulolytics, ammonifiers nitrifiers, aerobic nitrogen fixiers (Azotobacter) and anaerobic nitrogen fixiers (Clostridium) were studied. Metribuzin was found to inhibit soil respiration, causing statistically highly significant changes of that area of microbiological activity in almost all trial variants. The effect of metribuzin on microorganism abundance varied. It caused a decrease in total microflora, fungi, cellulolytics, nitrifiers, and aerobic and anaerobic nitrogen fixiers (Azotobacter and Clostridium) at all temperatures, and reduced the abundance of actinomycetes at 10?C and 30?C. No effect on ammonifiers was recorded.
U radu su predstavljeni višegodišnji rezultati istraživanja prisustva vrste Ambrosia artemisiifolia L. u korovskim zajednicama na teritoriji Republike Srpske. Snimanje korovske vegetacije vršeno je metodom Braun- Blanquet-a (1964). Ambrosia artemisiifolia L. je konstatovana u devet zajednica od kojih je najzastupljenija u asocijaciji Panico-Galinsogetum parviflorae Tüxen et Becker (1942). Posebno je značajno prisustvo u okopavinskim usjevima, strništu i višegodišnjim zasadima. U vinogradima Ambrosia artemisiifolia L. je prisutna u šest od ukupno devet zajednica gdje ima najveću pokrovnu vrijednost. Na sjevernom dijelu teritorije Republike Srpske izdvojen je facijes Panico-Galinsogetum ambrosiosum artemisiifoliae u kojem najveću brojnost i pokrovnost ima Ambrosia artemisiifolia L. Njeno masovno širenje je posljedica bioloških osobina, ulaska u agrofitocenoze, antropogenog uticaja i mnogo neobrađenih površina.
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